Young cynomolgus monkeys (Macaque cynomolgus) that were inoculated intracerebrally (IC) with "Biken" strain of Subacute Sclerosing Panencephalitis (SSPE) virus were monitored. Animals that were immunosuppressed died in seven days with an acute encephalitis. However, monkeys that did not receive immunosuppressive drugs have developed clinical signs of neurological damage 30 months after inoculation with the SSPE virus. Rubella antibody titers were high in the sera and spinal fluid of the affected animals. In our studies with human cytomegalovirus (CMV) in monkeys, we found that it is essential to use animals that are free of monkey CMV. Owl monkeys (Aotus trivirgatus) and patas (Erythrocebus patas) are utilized. We have developed fluorescence antibody techniques (FA) to quickly identify monkeys carrying monkey CMV. We are now identifying these negative animals and they will be infected with the human strain AD169 CMV.